I currently own a A200 body and a Sigma 70-300mm f4-5.6 APO Macro Super DG lens, used mainly for wildlife photography. I'm looking to upgrade my equipment but can't afford to do both the body and the lens at once. I've been looking at the A580 to upgrade the body and the new Tamron 70-300mm f4-5.6 SP Di USD Lens.

First off, do these seem like worthy upgrades from my current equipment?

And, which one would you get first as I may have to wait a while between purchases?

I must profess to not knowing too much about either lens, though they sound quite similar in spec...if upgrading lenses, I'd be tempted to look for a faster aperture or a longer reach - much depends on what you need.

Same goes for the body - the A580 will be a significant step up in some regards over the A200, but probably not too different in daylight IQ. So if you mostly shoot good daylight wildlife, it might not have a huge impact. However, shoot in mixed light, need higher ISOs, want faster burst, want live view option for off angles, or need to track moving subjects, and the A580 becomes quite a significant step up over your current cam.